A warewash machine is a utility dishwasher used in many restaurants, healthcare facilities and other locations to efficiently clean and sanitize cooking and eating articles, such as, dishes, pots, pans, utensils and other cooking equipment. Soiled articles are placed on racks and provided to a washing chamber of the warewash machine. In the chamber, cleaning products and a rinse agent are applied to the articles over a predefined period of time referred to as a “wash cycle,” which includes a cleaning cycle and a rinsing cycle. The cleaning products are typically chemical solutions formed by dissolving one or more component chemical products in the rinse agent. The term component chemical product is used broadly herein to encompass, without limitation, any type of detergent, soap or any other product used for cleaning and/or sanitizing. The rinse agent typically is water, and may include wetting and/or sanitizing agents.
The article racks contain holes that enable the cleaning product, the rinse agent and soil washed from the articles to pass through the racks during the wash cycle and to a solution tank located on the underside of the warewash machine. At the end of the wash cycle, the rack is removed from the washing chamber so that other racks carrying other soiled articles may be moved into the washing chamber. The wash cycle is then repeated for each of these subsequent racks. Wash cycles may be customized for specific types of racks and the articles that the racks carry.
The cleaning product (hereinafter, “chemical solution”) is formed within the solution tank from the combination of the rinse agent, which initially is dispensed into the solution tank prior to the introduction of any article racks and subsequently dispensed thereto during the rinsing cycles, and a component chemical product directly input to the solution tank. A wash module is provided above the solution tank and in the lower portion of the washing chamber. The wash module extracts the chemical solution from the tank and applies the solution to the rack (and hence, the articles contained therein) during the cleaning cycle. Following the cleaning cycle, a rinse module, which is provided in the upper portion of the washing chamber, administers the rinsing cycle by applying a rinse agent to the articles thereby rinsing the chemical solution from the articles. During both the cleaning and rinsing cycles soil (e.g., food particles) is dislodged from the articles in the racks and washed into the solution tank to combine with the chemical solution.
Percent concentration of each individual component chemical product within a chemical solution being used by a warewash machine to clean and sanitize articles at a public facility is governed by various food and health regulations. The percent concentration of a particular component chemical product relative to a formed chemical solution is proportional to the mass of the component relative to the mass of the rinse agent in the chemical solution. One generally accepted method for complying with these regulations involves controlling input of the component chemical product to the solution tank based on conductivity measurements of the chemical solution. These conductivity measurements generally represent the electrical behavior of the chemical solution, i.e., the ionic concentration of the solution relative to pure water.
To meet the above-noted various food and health regulations, warewash controllers are employed to oversee operations performed during the wash cycles of conventional warewash machines. Warewash controllers are often added to warewash machines after the machines are deployed into a production environment in which the machines are intended for use. The warewash controllers are communicatively coupled to the rinse and wash modules such that control over operations of these modules is administered by the controller. The warewash controller may also be communicatively coupled to a component dispenser and operable to control the component dispenser to dispense specified amounts of a component chemical product to the solution tank and/or wash chamber. Alternatively, the controller for the component dispenser may be separate from the warewash controller. Regardless of implementation, the basic function for controlling the component dispenser involves sensing information related to operation of the warewash machine and using this sensed information to operate the component dispenser in such a manner that the various food and health regulations are complied with.
Inductive probes or conductivity cells may both be used to measure the ionic concentration of a chemical solution within the solution tank. Typically, these probes or cells gather such information by sampling, preferably multiple times, the chemical solution in the solution tank to generate therefrom an electrical parameter (e.g., conductance or resistance) indicative of the ionic concentration of the chemical solution relative to pure water. This electrical parameter renders an associated conductivity reading for the chemical solution. The associated conductivity reading represents an estimated percent concentration of the component chemical product relative to the rinse agent in the chemical solution. Based on this calculation, the controller controlling the component dispenser controls the dispensing of the component chemical product in order to force the percent concentration of that component chemical product in the chemical solution to a level prescribed by governing regulations.
While using conductivity measurements to control product concentration in a chemical solution has proven to be an effective practice for complying with the various governing food and health regulations, these conductivity measurements are not entirely accurate readings of the actual percent concentration of the product in the solution. In addition to ions associated with the component chemical product, a chemical solution typically includes ions associated with the water used for the rinse agent as well as ions associated with the soil washed from the articles placed in the warewash machine. Both water and soil therefore contribute to the ionic concentration of a particular chemical solution, and as such the determined conductivity is not a true measure of the percent concentration of a component chemical product contained in the solution.